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Патент USA US3036225

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May 22, 1962
R. N. JONES ET AL
3,036,215
SPECTROMETRIC CELL STRUCTURE
Filed April 30, 1959
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May 22, 1962
3,036,215
R. N. JONES ET AL
SFECTROMETRIC CELL STRUCTURE
Filed April 30, 1959
3 Sheets-Sheet 2
/6
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3,93 6,2 l 5
Patented May 22, 1962
2
3,036,215
SPECTRGMETRIC CELL STRUCTURE
Richard N. Jones, Ottawa, Ontario, and Joseph M. A.
Nadeau, Hail, Quebec, Canada, assignors to National
Research Council, ()ttawa, Ontario, Canada, a body
corporate of Canada
Filed Apr. 30, 195'9, Ser. No. 810,141
Claims priority, application Canada June 3, 1958
4 Claims. (Cl. 250—43.5)
calcium and lead halides; also arsenic trisulphide. Sodium
chloride in the form of natural or synthetic rock salt is
the most readily available material commercially. When
rock salt is used, there is a requirement that it must be
in the form of a single crystal, but there is no diliiculty
in obtaining crystals of rock salt of su?icient size, since
they can be readily synthesized. Typical dimensions for
This invention relates to the construction of cells of the
type employed for mounting specimens for spectrometric
examination.
materials are known. These are normally chosen from
the alkali metal halides, although a silver halide is some
times used. Other materials that may be used are barium,
The use of spectral analysis, particularly
infra-red spectral analysis, is now a well~established lab
a cell-containing device of this type would be about two
centimeters long, one centimeter wide and 0.5 centimeter
thick. Pieces of rock salt crystal of this comparatively
small size are readily available as scrap left over from the
oratory technique for the identi?cation. of organic com 15 manufacture of larger optical bodies.
pounds, and infra-red spectrometers have become standard
If ultra-violet or visible radiation is to be employed
equipment in most laboratories concerned with organic
in the spectrometer, the material of the carrier body may
chemical analysis.
be quartz crystal, or in some cases one of the optical
The preferred method at present in use for mounting a
glasses available and having suitable optical transparency.
sample in a spectrometer is to dissolve the sample in a 20
It will be assumed, however, for the purposes of the
suitable solvent, and then introduce resulting specimen
subsequent speci?c description, that infra-red spectrometry
into a cell-containing device which is mounted in the
spectrometer. The term “sample” is used herein to denote
the material for analysis; the term “specimen” is used to
is concerned and that the cell-containing device is formed
from rock salt, since, although the invention is essentially
- su?‘iciently broad in scope to include the other forms of
denote the combination of sample and vehicle that is 25 radiation and other materials indicated above, infra-red
placed in the cell for examination in the spectrometer.
spectrometry is by far the most common form of spec
The basic requirements for the solvent that is used as the
trometry employed and rock salt is the most convenient
vehicle are that it should be chemically inert both towards
material to employ.
'
the sample and towards the material of which the cell-con
In our previous United States Patent 2,927,209, issued
taining device is constructed. Also, of course, the sam 30 March 1, 1960, there is disclosed a device containing a
ple must be su?iciently soluble in the solvent. Moreover,
cell which may be of a size suitable for containing a
it is necessary that the solvent have satisfactory optical
“macroscopic” sample (about 1 milligram); a “micro
properties, that is, it must be optically transparent to the
scopic” sample (about 100 micrograms) or an “ultra
radiation being employed in the spectrometer. To be
microscopic” sample (50 micrograms or below).
optically transparent the solvent must not only transmit 35 The present invention is concerned with cell structures
the radiation employed in the spectrometer, but it must
designed for use with specimens containing samples in the
not modify such radiation to any appreciable extent, since
macroscopic‘ and microscopic ranges, but not in the ultra
any such modi?cation would swamp the characteristic
microscopic range. In the ultra-microscopic range, the
spectral modi?cations imparted to the radiation by the
specimen is so small that the shape of the cell is of little
sample in solution.
or no importance. With the larger specimens involved
The present invention is concerned with improvements
with microscopic and macroscopic samples, however, the
in the construction of devices which contain a cell in which
shape of the cell becomes important. In particular, it
such a specimen can be mounted in a spectrometer for
becomes necessary for satisfactory optical performance
spectral analysis. Cell-containing devices in use at the
'to provide-the cell with a pair of planar side walls, paral
present time are of comparatively complex structure usual; 45 lel to one another, through which the radiation enters and
ly involving many separate pieces of different materials,
leaves the cell. It is principally this requirement that has
often including precision made metal parts fabricated into
led to the comparatively complex construction previously
a complex assembly. As a result, these devices are expen
employed in most cell-containing devices. With few ex
sive, and it is only economical for a laboratory to keep
ceptions, devices in current use consist essentially of a
on hand a comparatively small number of them. They 50 pair of ?at plates of optically transparent material sep
must be thoroughly washed out after each use and care
arated by a spacer. Access to the cell cavity is' provided
fully stored for further use. This economic need for the
by holes drilled through the edge of the spacer, or through
frequent reuse of known cell~containing devices is also
the face of one of the windows. Unless carefully con
disadvantageous in that it reduces the utilization of the
structed and maintained, such devices are subject to leak
spectrometer, since this instrument will normally have to 55 age. If the windows and spacers are sealed with a chem
remain idle while each cell-containing device or a group
ical adhesive, leaks may develop through attack on the ad
of such devices is washed out and recharged with a new
hesive by the solvent, and ‘products extracted from the ad
hesive may contaminate the sample and invalidate the spec
' trum.
A principal object of the presentinvention is to provide
In cell-containing devices of more recent design,
an improved cell-containing device that will be consid 60 these difficulties have been overcome by careful polishing
specimen.
_
_
'
era-bly simpler than existing devices, and consequently
cheaper to manufacture, while still performing satisfac
‘and machining of ‘the component parts so that a leak re
"sistant seal between cell window and spacer can be
torily in the spectrometer. By cheapening the manufac
achieved by the application of pressure alone. V-Such- cells,
however, are expensive to produce, and their servicing and
ture of such devices, it becomes practicable for a labora
tory to have on hand su?’icient of the devices for a large 65 replacement is a signi?cant economic ?actor on the main
tenance of an infra-red spectrometer in routineoper-ation.
number of them to be charged in advance and fed into the
spectrometer without delay, thus obtaining maximum
In contrast to such complex structures, the present in
vention comprises a unitary body formed from a single
utilization of this expensive instrument and of the time
of the skilled technician who operates it.
i
piece of material,‘ said body being provided with a cell
cavity having a pair of planar faces extending parallel
If an infra-red examination is to be made, the cell
containing device will be made of a material optically 70 to each other. To form such a device it is necessary’to
transparent to infra-red radiation. Numerous suitable
hollow out the material into an elongated cavity of rec
3,036,215
3
4
tangular cross-section or other cross-section having a‘
larger cross-sectional dimension) of the rectangular cell
pair of ?at and parallel ‘opposite faces. This can be done
13. When these two cavities have been made,’the two
parts 10a and 10b of the body are brought together and
bonded; To eifect this bonding the contact surfaces of
by the impact grinding technique described below.
Forfurther details, reference is directed to the accom
the two parts of the body are smoothed, moistened with
saturated aqueous sodium chloride solution, placed to
gether and then clamped under pressure with heating to
110° C. for twelve hours. Strong bonds between two
panying drawings which, illustrate-three forms of cell-con
taining device constructed in accordance with the pres
ent invention.
.
FIGURE 1 is an‘eXploded perspective view of a ?rst
bodies of rock salt can be obtained in this manner and the
bond will resist'cleavage at temperatures up to 200° C.
The bonded surface is not optically clear, but this is no
disadvantage, since this surface is not placed in the optical
II—II in FIGURE 3;
1 7
beam in the spectrometer. Stopper 17 is provided to
FIGURE 3 is a transverse section takenv on the line
close neck 16. This second construction has the ad
III-—IIl in FIGURE 2;
'
FIGURE 4 is an exploded perspective view of a sec 15 vantage over the construction shown in FIGURES l-3
that the neck 16 is of smaller diameter than the neck 11
ond cell-containing device according to the invention;
‘and can thus be more effectively sealed. With the wider
FIGURE 5 is a central vertical section of the main
neck of the ?rst embodimentit is more dif?cult to avoid
. portion of the device seen in FIGURE 4 taken on'line ,
solvent evaporation and greater care must be exercised
‘ V—-V in FIGURE 6;
'
FIGURE 6 is a ‘transverse section taken on the line 20 to ensure a tightly ?tting stopper while the cell is in use.
On the other hand, the ?rst embodiment is cheaper to
VI-—-VI in FIGURE 5; a '
manufacture as not involving the two-part construction
FIGURE 7 is a front elevation’ view of a third form
form of cell-containing device; I
'
FIGURE 2 is a central vertical section of the main
portion of the device seen in FGURE 1 taken onrline
and bonding step.
of cell-containing device constructed in accordance with
FIGURE 8 ‘is a transverse section taken on the line
VVII'L-VIII in FIGURE 7; and
FIGURE 9 is a vertical central section taken 011th
line IX-IX in FIGURE 7.
. V ’
In both types of cell-containing device so far described
the thickness of the cell (i.e. the smaller of the two di
mensions in cross-section, the distance between faces 14
and 15) is ‘approximately one millimeter. This is a sub
stantial distance for the radiation to traverse through the
specimens and as a result these cells ‘are satisfactory with
V the ‘present'invention;
~
The device seen in FIGURES 1-3 consists of an elon
gated body 10 of a single crystal of rock salt drilled cen 30 comparatively dilute solutions. With solutions of greater
opacity, it is desirable to have a shorter optical path
trally to provide a?rst cavity 11, which will be referred
l to as the “nec . ”
through the specimen if good results are to be obtained '
This neck 11 is of circular cross-sec
in the spectrometer. It is possible to form cavities nar
tion and serves to receive a stopper 12 (shown only in
FIGURE 1) formed of a resilient material inert both to 35 rower than 1 millimeter in rock salt by the ultrasonic
drilling technique, but the bits employed become very
'to’ solvent and to the rock salt. A suitable material is
thin and delicate and tend to deform during the grinding
the synthetic resin known under the trademark Te?on.
process producing curved cavities that are no longer par
Inwardly of the neck 11 and communicating therewith
allel with the outside faces of the body. This isundesir
is a second cavity 15 which constitutes the cell itself. This
'
cell 13 is rectangular in cross-section so as to provide a 40 able for optical reasons.
This dit?culty can be overcome by adopting the shape
pair of parallel planar faces Hand 15' (FIGURE 3).
of cavity illustrated in the third embodiment shown in
Whereas the neck 11 is formed by conventional drilling,
FIGURES 7~9, where a cavity is formed with a cross-sec
the cell 713» is formed by ultrasonic impact grinding.’ The
general technique for producing small cavities in brittle . tion of dumb-bell shape. A dumb-bell bit is employed
materials by ultrasonic impact grinding has been de
comprising a pair of rounded side members of approxi
etched appearance. A preliminary polish is obtained by
repeating the drilling processwith a slightly larger bit'
and a ?ne emery powder. ,A ?nal smooth surface is
achieved. by ?ushing out the cell rapidly with 50% aque
jous ethanol followed immediately by absolute ethanol.
For best optical properties, the outer faces 24 and 25
ultrasonic impact grinding technique, because of the rigid
' scribed by M. S. Hartley in Electronics, I anuary 1956, 4.5 mately 0.75 millimeter diameter connected by a cross-bar
,of approximately 0.1 millimeter thickness to form the
pages 132-135. A bit of approximately the cross-section '
actual functional slot portion of the cell cavity. Such a
t, of the cavity to be made is pressed down against the ma
bit forms a cell cavity of complex shape having a pair
terial while being oscillated at an ultrasonic frequency of
of cylindrical chambers 17 and 18 joined by a slot por
25 kilocycles. Initially a cavity is producedrusing, a
slightly undersized mild steelbit fedwith No. '218 mesh 50 tion 19 which is very narrow in comparison with the cells
13 of the‘previous embodiments. Nevertheless such a
Carborundum abrasive suspended in absolute ethanol.
cavity can be formed with planar parallel faces by the
The walls of thecavity so produced have a coarsely
ity imparted to the bit that forms the cavity by the cylin
drical portions of that bit which forms chambers 17 and
18.
_
of the body 10 will be ground and polished parallel to one
‘ another 'and'the faces 24 and 25 will be parallel to faces 60
'14 and 15. Some deviation in the planarity and paral
' lelism of faces 14 and 15 can ‘be tolerated.
In a spec»
trometer' the radiation will pass through‘ the device as
I I’ demonstrated by the ‘arrows R.
A modi?ed form of cell is illustrated in FIGURES 4-6.
In this case the body of the ‘cell-containing device is
formed, in two parts, a lower main, specimen-mounting
part, 10av and an upper part',10b.; Before parts 10a and
10b are joinedntogether, a rectangular cell cavity13i is
65
.
a
-
In use the optical beam traverses only the functional
slot portion 19, of the cell cavity, this slot having parallel
planar faces 14 and 15 as before. As in the case of the
structure shown in FIGURES 4-6, the body of the device
shown in FIGURES 7-9 is made in two parts a lower
part 10a and an upper closure parts 10b.‘ The upper part
10b'is formed with ‘a pair of circular, holes 20 each to
receive a- Te?on stopper 21. In manufacture thetwo
parts 10a and 10b are bonded together in a manner simi
,lar to that alreadydescribed, the holes 20 being in reg
ister wtih chambers 17 'andI18 to enable the cell cavity
. to be ?lled and there being no slot in theclosure part 1%
equivalent ‘to. the slot 19. In order‘to avoid capillary
?ow of sodium chloride solution. down the ‘slot 19 during
I ,: formed in the lower body part 10a by impact grinding
the bonding process, the upper end of such slot is en- '
in the same manner as just described. Parallel planar
. larged into semi-circular cross-section as shown at 22.
faces 14 and 15 are thus provided as before.- Indepen
dently of this operation a neck hole 16.is formed in the ‘I When this device isl?lled with a specimen, the two cylin
dticalehambers 17 and 18 represent an appreciable para
. upper body part 10b; This has to'be done separately’ as 1
a , the diameter of the neck 16 is smaller than’, the
(the 75‘ sitic volume, but the capillary action of the very narrow
3,036,215
6
slot 19 is such that it will remain ?lled with liquid even
when the cylindrical chambers are themselves only partly
?lled or even empty. In this way the parasitic volume, if
it should be disadvantageous, can be almost wholly elimi
nated by placing only enough specimen in the device to
?ll the slot 19.
We claim:
1. A device ‘for mounting a liquid specimen for spec
faces parallel to each other and disposed so close to each
other as to de?ne a narrow slot portion in which said
liquid specimen will be retained by capillary action.
3. A device for mounting a liquid specimen for spec
trometric examination, at least the specimen-mounting
portion of said device comprising a unitary body formed
from a single piece of a material chemically inert to the
specimen and optically transparent to the radiation of the
spectrometer, said body being provided with a cell cavity
trometric examination, at least the specimen-mounting
portion of said device comprising a unitary body formed 10 for containing said specimen, said cavity having a pair
from a single piece of a material chemically inert to the
of planar faces extending parallel to each other to de
specimen and optically transparent to the radiation of the
?ne a slot portion therebetween, the width of said slot
spectrometer, said body being provided with a cell cavity
portion as determined by the spacing apart of said faces
for containing said specimen, said cell cavity having an
being of capillary dimension While the length and
elongated chamber ‘and a narrow slot portion, one edge 15 breadth of said slot portion as determined by the extent
of said slot portion opening into and communicating with
of said faces in their own planes both being substantially
said elongated chamber along the length thereof, said slot
greater than capillary dimension whereby a sheet of said
portion being de?ned by a pair of planar, mutually paral
liquid specimen having only one dimension of capillary
lel faces disposed so close together that liquid specimen
size will be retained by capillary action in said slot por
will be retained for spectrometric examination in said slot 20 tion. '
portion by capillary action even when the total volume
4. A device as claimed in claim 3, wherein said slot
of said specimen is insu?icient to ?ll said chamber to the
portion communicates with at least one other portion of
same level ‘as said slot, said chamber being too wide to
said cell cavity, 211- the dimensions of said other portion
retain liquid specimen therein by capillary action, the
being greater than capillary in size whereby such other
dimensions of said slot portion as determined by the ex 25 portion provides a substantial space non-competitive with
tent of said ‘faces in their own planes being substantially
said slot portion ‘for the volume of liquid specimen re
greater than capillary size.
quired to charge said slot portion but available to contain
2. A device for mounting a liquid specimen for spectro
liquid specimen in excess of said volume.
metric examination, at least the specimen-mounting por
tion of said device comprising a unitary body ‘formed 30
References Cited in the ?le of this patent
from a single piece of a material chemically inert to the
UNITED STATES PATENTS
specimen and optically transparent to the radiation of
2,857,524
Talbern et al ___________ __ Oct. 21, 1958
the spectrometer, said body being provided with a cell
cavity for containing said specimen, said cell cavity being
of ‘dumbbell shape in cross-section, the central portion of
such dumb-‘bell shape being de?ned by a pair of planar
2,927,209
Jones et ‘a1. ___________ __ Mar. 1, 1960
679,711
Great Britain _________ __ Sept. 24, 1952
FOREIGN PATENTS
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